The invention relates generally to an electrical heating system for footwear and specifically to a universal heater useful for shoes or boots.
Wearers of footwear who expose themselves for long periods to cold, generally experience the discomfort of having cold feet. It has been desirable to provide devices for heating shoes or boots in order to permit the outdoor sportsman or those who must work for extended periods in the cold to be able to warm their feet periodically. Therefore, to provide a practical cost-effective solution to this problem has been the goal of many devices that have been proposed.
It has been proposed to provide a heated sock. This device is generally bulky and relatively expensive and requires frequent washings. This limits its useful life. Most sportsmen prefer wearing clean socks daily. The use of a heated sock would require that the individual own a number of pairs of socks, and accordingly the cost of acquiring them becomes prohibitive. In addition, the bulk of such socks prohibits them from being used in many sports where a thin sock is essential for foot control, such as in skiing.
Another approach to this problem has been the suqqestion for providing heated insoles. Such devices do not require washing or changing and can be installed in any shoe as an accessory. The difficulty in employing such devices is that a wire lead must run from the insole to a battery pack, which must be mounted somewhere on the person or on the footwearer itself. If a long lead is used, a substantial amount of electrical energy may be lost in the lead. Also the lead may be prone to breakage since it is subject to continuous flexure during body motion. Most insole heating devices have frequent lead breakage problems. These problems occur due to the lead length and the placement of the lead in areas of the footwear subject to repeated flexure.
It has been proposed to run a wire in a heated insole device up the leg of the wearer to a battery pack strapped to the leg or the waist. Generally, this proposal has not been successful since people prefer not to have wires running up their body merely for the comfort of a heated shoe.
In ski boots, some of these problems are solved due to the nature of the design of the conventional ski boot. Such boots generally have a thick exterior shell which is relatively strong and easily supports the weight of the battery pack. In addition, they have a removable liner or bladder, which is typically a half-inch thick and can cushion large long interconnecting wires, which run from a battery pack to a heating element. In distinction with ski boots, general footwear have thinner pliable material which generally prevents wires from being placed in desirable locations, since they do create discomfort to the user.
In order to provide a universally adaptable shoe heater, a number of problems must therefore be overcome. The device must be small yet be an efficient heating element which can be easily installed into a shoe without causing discomfort, and preferably without any noticeable change in the feeling of the shoe fit. Additionally, the interconnection between the heating element and a power supply must be such as not to cause any change in fit or any noticeable change in the feeling of the shoe fit. The location for mounting a power supply must be such that it will not impede the normal function or use of the shoe and will not become easily dislodged during use. The entire heating device must be such that it can be installed by a user and require little time and effort to accomplish the installation. The installation should be such that no damage is done to the shoe and the device should be removable with very little or no evidence of its previous installation. The heating device should also be such that it is not easily broken or damaged in the normal functioning of it by the user or in the activity for which the footwear is used. The heating device should also be removable for replacement or repair. Also, the time required for removing the power supply should be very little in the event the user decides he/she does not desire further heating to take place.